40
Exception Code
Name
Cause
1
Bad function code
Function code is not supported
by the controller
Illegal data address
Illegal data value
Register address out of range
Data value out of range or
attempt to write a read-only or
protected data
2
3
7-2 Exception Responses
If the controller receives a message which contains a corrupted character (parity check error, framing error etc.), or if
the CRC16 check fails, the controller ignores the message. However, if the controller receives a syntactically correct
message which contains an illegal value, it will send an exception response, consisting of five bytes as follows:
slave aoffset function code + exception code + CRC16 Hi + CRC16 Lo
Where the offset function code is obtained by adding the function code with 128 (ie. function 3 becomes H'83), and
the exception code is equal to the value contained in the following table:
